1. Field of the Invention
The present invention relates to a detection device of a planar area and a stereo camera system both of which detect a planar area from an image from an imaging element for vehicle mounting.
2. Background Art
Recognition methods of traveling environments can be broadly classified into a method using a laser radar, ultrasonic waves, or a millimeter wave radar, and a method using an image.
The detection method using the laser radar or the millimeter wave radar is problematic in that, in general, devices were expensive and sufficient spatial resolution could not be obtained. The detection method using an ultrasonic sensor is problematic in that the measurement of far distance was difficult, and spatial resolving power was low.
The methods using an image can be classified into a method using an image obtained from a single eye, namely, one viewpoint, and a method using compound eyes. Conventionally, many of the methods using an image adopt the single eye, and are mainly assumed to be used under developed environments such as an expressway, and such methods detect a travelable area through detection of a white line of a road surface (e.g., a demarcation line or a halfway line) and the like. However, on a general road, in a parking space, or the like where the presence of the white line and the like was not guaranteed, and various road surface colors or patterns appeared, there was a problem that it was difficult to stably distinguish the travelable area from an obstacle based only on a density pattern.
Meanwhile, in the method involving the use of the compound eyes, namely, a detection method using stereo images, in principle, since a three-dimensional configuration of an environment can be used; it is likely that a traveling environment can be recognized more stably. In particular, since the travelable area can be seen as generally plane in the space, for example, Patent Document 1 (JP Patent Publication (Kokai) No. 2000-293698 A) and Patent Document 2 (JP Patent Publication (Kokai) No. 2005-217883 A) have already proposed a method in which projection transform is performed on images, and based on an overlapping degree of the respective images, it is detected whether or not a traveling environment is a planar area, or whether or not such traveling environment is an obstacle. In addition, the aforementioned documents have also proposed a method in which when calculating a projection transform function, an equation of the plane is obtained at the same time.